Two-way-signaling system



Aug. 7, 1923. Mams? R. A. l--IEISINGl TWO-WAY SIGNALING SYSTEM Filed Aug. '7, 1920 Raymond A. Heiss/'m9, by my.

Patented Aug. T, i923.

narran stares rnlreur ermee. f

turen RAYMOND A. HISING, F EAST ORANGE, NEW JERSEY, `ASSIGrNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NEW YORK, N. Y., A. CORPORATION OIF or new Yoan.

TWO-WAY-SXGNALING SYSTEM.

Application tiled August t, 1920. Serial No. 401,888.

To all whom it may concern:

Be it-known that l, RAYMOND A.. HEIsNe, a citizen of the United States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certa-in new and useful Improvements in 'llwo-lVay-Signaling Systems, of which the following` is a iull, clear, concise, and exact description. The present invention relates to two-way l0 signaling circuits. More particularly, the invention relates to ntwo-way transmitting and receiving circuits in which the transmitter and the receiver are both permanently associated with the same circuit, and l5 has for an object the reduction or elimination of the response of the receiver to energy in the local transmitter circuit.

ln signaling systems employing modulated waves, it is common to provide a modulator by which the high frequency or carrier waves or currents are controlled in accordance with the signals to be transmitted, and a detector or. demodulator for deriving from a received signal-modulated wave, the current component representing the signal to be received. .ln such systems, balanced circuits are usually provided for making the detector neutral with respect to the modulator so that the high-frequency modulated energy from the output of the modulator does not enter the local detector circuit. ln an application of H. W. Nichols, Serial No. 326,493, filed September 26, 1919, asystem is disclosed in which a single highfrequency set is used for both modulating and detecting, and this set is connected to the line or to the antenna through a single coupling or tuned circuit or filter, thus dispensing with the high frequency balance. ln some cases, however, and more particularly where the ratio of transmitted to received energy is large, the side tone in the receiver of such a system, that is, the response of the receiver to energy in the local transmitter, may be large. This side tone can not be reduced or eliminated by high frequency balancing circuits in a system of this character, since the same element, for example, a discharge device of the usual three 'element vacuum tube type, serves to act both u on the. outging high frequency ener an the incoming Vmodu ated energy, and t e receiver and transmitter are both permanently connected to 'this element. The

present invention provides a balance between the transmitter and the receiver preferably by controlling currents of the signaling requencies instead of the modulated high frequencies and is, therefore, particularly applicable to a system of the type indicated in which both the transmitter and receiver-are associated withvthe same highfrequency set.

Although the energy transfer between the transmitter and the local receiver is spoken lof as side-tone, it does not necessarily appear as intelligible sound but may give any kind of a response depending upon the type of receiver used, and this term, as used throughout the present specification and as commonly used in the art, is as applicable to a telegraph receiver for instance, as to a telephone receiver.

lln the drawing, Fig. 1 illustrates. dial grammatically one form of the invention as 'applied to a radio telephone system, and

1F ig. 2 shows a somewhat .different circuit' arrangement embodying the invention in a high frequency wire telephone system.

lln li' ig. 1, a modulating system of the type commonly known as the constant current modulating system and including an oscillator 0 and a modulator M, is coupled to the antenna 1' through the power amplifier A. The oscillator itself, comprises a discharge tube 2, which may be of thel usual construction and has a filament, a grid and a plate connected to dierent oints of the oscillatory circuit comprised or inductances 3 and 4l, and variable capacity 5. By means of the condenser 5, the period at which the tube oscillates ma `be controlled at will.-

The modulator comprises a' discharge tube similar in construction to 2, and space current from the source' 6 is supplied to the tubes 2 and 8 in parallel through the high inductance choke coil 7. rlhe inductance of this choke coil is so great that current variations of frequencies of the .order ot those used in speech are not transmitted through the coil. In the space current path for the tube 8, an additional choke coil 9 is provided having such an inductance as to freely pass'currents of voice frequency but to exclude from the circuit of the tube 8 currents of the high frequency generated by the oscillator 0. The impedance of the tube 8 may be varied in accordance with speech waves impressed upon the circuit of the grid or impedance control element through the transformer 10 from the speech current circuit 11, which is shown as containing a microphone transmitter T. Changes in the impedance of the tube 8 cause variations in current through the tube from the source 6 and since'the large choke coil 7 keeps the total space current supplied to the tubes 2 and-8 in parallel practically constant, a curf rent change is produced in the plate circuit of the tube 2 which is substantially complementary to that\produced in the space current of the modulator M The amplitude of the output Wave from the oscillator 0 is, therefore, varied in accordance with speech.

'This particular method of modulatin the high frequency wave forms no part o the present invention, which is not dependent upon any particular sfystem of modulation as will appear hereina ter, but for purposes of illustration this system of modulation whichris Well adapted for use with the present invention has been shown and described.

The modulated output current from the oscillator O is impressed upon the amplifier A, by means of a coil 12 yinductively related to the coil 4 of the oscillator. The output circuit of the amplifier is, coupled to the antenna 1 by means of the variable-inductive A couplin 14l and contains a condenser 15 which s old be of such a size Aas tof'oifer negligible impedance to currents of the frequencygenerated by the oscillator O but to offer high impedance to currents of the voice frequencies or other signaling frequency.

The space current for the amplifier Avis supplied from the battery 13 through a receiver R, the battery and receiver being connected in shunt to the condenser 15. Ihe action of this much of the circuit is that a certain degree of detection of the modulated high frequency wave takes place in the amplifier A whether the wave is being transmitted to the antenna 1 or is being received from the antenna 1 intheplate circuit of the amplif fier. s This is probably due to a slight curvature of that portion of the tube characteristic over which the amplifier A operates. The low frequency or signaling component resulting from this detecting action of the amplifier is heard in the receiver R. l

In the case of Va radio system, the energy transmitted is enormously large compared with the energy received and the sounds heard inthe receiver R, due to currents in the transmitter circuit 11, are liable to be very loud. In accordance with the invention, this side tone is reduced or eliminated by means of a neutralizing circuit connected between the circuit 11 and the circuit of the receivf* R and including the electron discharge device 16. B means Aof this current path, energy from t e transmitting circuit 11 is transferred directly to the receiver circuit. By means of the variable coupling 17,v the desired amount of current in this circuit vcan be impressed upon the receiver, and the phase of the impressed current may be made such as to oppose current in the receiver R which results from detection of the transmittedwave in the amplifier A. The main purpose of the discharge device 16 is to prevent the passage of current from the receiver circuit to the transmitting circuit 11 which might, under certain circumstances, produce slnging of the system. The dischar e device 16 being a uni-laterally conductlng element prevents the 'passage of a signal except in the direction from the transmltting to the receiving circuit. The device 16 may be an amplifier if desired and may be controlled to amplify the currents impressed upon the receiver'through the coupling 17 The high frequencywaves received from ,the distant station will be detected by the amplier A and received in the receiver R With-v out producing any effect upon the neutralizing current path. By properly adjustingI the constants of the current path and the phases Vof the currents, the signal .heard in the receivervvhen a message is beings transmitted from the local station may be made to have substantially the same degree of l'oudness as the received signals, or the side tone may be eliminated altogether if desired. In Fig. 2 isshown diagrammatically, a complete two-Way circuit arrangement at station S on the high frequency telephone line L. The oscillator Or is of a well-known type and has its frequency controlled by a variable condenser 5 as in the case of the previously described oscillator circuit. The oscillator is coupled, by means of the coil 4, to the input circuit of a three-element modulatin l tube M and speech Waves from the circuit 11 are, at the same' time, impressed upon the input circuit of the modulator through the coupling 10. For receiving the the modulator. ln this case, n'o amplier for the modulated waves is shown but it is obvious that an amplifier may be used and in practice probably would be desirable, in 11G Whlch case the receiver R would be connected to the output circuit of the amplifier as in the case 'of Fig. l. A neutralizing circuit including the discharge device 16 is provided, as before, between the transmitting circuit 11 and the receiving circuit. The frequency of the carrier wave used in the circuit of Fig. 2, is presumed to be lower than the carrier frequency used in Fig. 1 although no definite relation need exist between the frequencies used in the radio system and those used on the line. If the carrier wave is only slightly above the upper limits of audibility, the modulated vvave may comprise a frequency range representing a con- Memos? .5 siderable percentage ofthe carrier-wave frequency itself, andv for the purpose of transwith the line L. The 'operation of the system of F ig. 2 is substantially the same as that of the circuit of Fig. l. Other stations,

' similar to that shown at S, may be provided on the line L and each pair of stations would, as is well understood, employ dierent carrier Wave frequencies. A tap connection for another station, S, is indicated in the drawing. v

Although the invention has been illustrated and described as embodied in a telephone system, it is evident that it is clearly applicable to other types of signaling or of 4transmission in which the response of a receiver t'o energy in the transmitting circuit is to be reduced or eliminated. The scope of the invention is dened in the following claims.

What is claimed is:

l.V In -a two-way modulated wave signaling system, a repeating device for transmitting a high frequency wave modulated in accordance with signaling-frequency currents and for translating modulations of a high frequency wave into signaling currents, a transmitter and a. receiver for signaling frequency currents associated with said repeating device, and means for reducing the effect on said receiver of currents of signaling frequency in said transmitter comprising a circuit between said transmitter and receiver for impressing signaling currents from said transmitter upon said receiver.

2. In a two-way signaling system employing modulated waves of ultra-audible frequency, a comm-on electric discharge tube circuit for translating currents of audible frequency into variations of ultra-audible frequency and vice versa a transmitter and a receiver for currents of audible frequency associated with said circuit, and means for reducing the effect in said receiver of current in said transmitter'impressed through the medium of said circuit comprising a neutralizing path for transmitting current of audible frequency from said transmitter to said receiver of such phase as to oppose the current in said receiver impressed through the medium of said circuit.

3'. In a two-way system, a discharge device, a transmitting means for impressing high frequency Waves upon said device for transmission, means for impressing received mission comprising a circuit independent of said discharge device for transmitting neutralizing current from said transmitting means to said receiver.

4. lin a two-Way signaling system, a circuit for supplying high-frequency modulated waves for transmission, including a discharge device and a circuit for impressing energy thereupon including a. telephone transmitter, said discharge device acting to transmit high-frequency waves and to detect both transmitted and receivedl high frequency waves, a telephone receiver associated with the output circuit of said discharge device for receiving the detected component of the high-frequency waves, and means for reducing' the side-tone in said telephone receiver comprising a circuit, connected between said transmitter and said receiver, for supplying to said receiver currents substantiallyopposite in phase to the currents impressed upon said receiver from said transmitter through said device.

5. ln a two-way signaling system, a circuit for supplying high-frequency modulated Waves for transmission, including a discharge device and a circuit for impressing energy thereupon including a telephone transmitter, said discharge device acting to transmit high-frequency waves and to detect both transmitted. and received high-frequency waves, a telephone receiver associated with the output circuit of said discharge device for receiving the detected component of the high-frequency waves, and means for reducing the side-tonein said telephone receiver comprising a circuit, connected between said transmitter and said receiver, for supplying to said receiver currents substantially opposite in phase to the currents impressed upon said receiver from said transmitter through said device, said last mentioned circuit comprising a discharge device for permitting current to pass only in one direction between said transmitter and said receiver.

6. ln a signaling system, a. common transmitting and receiving electric discharge tube, a transmitter for impressing current uponsaid tube and a receiver for receiving current of the same order of frequency from said tube, a connection between said transmitter and said receiver for neutralizing at least partially the eect in said receiver of current impressed ,on -said tube from said transmitter and means for preventing the system from singing comprising a uniaterally conducting element in said connection.

7. ln a two-way modulated wave signaling system, a wave repeater for transmitting and receiving modulated waves, a signalingfrequency transmitter and a signaling-frequency .receiver associated with said wave repeater, and a uni-laterally conductln circuit between said transmitter and sai rerio ceiver for transmitting energy -from said transmitter to said receiver. v

8. A modulated wave signaling system comprising means including a transmltting instrument and a vacuum tube for roducing and modulating a carrier wave or signal transmission, means including a receiving instrument and said vacuum tube for detecting a modulated carrier wave for signal reception, and means controlled by said transmitting instrument for reducing the side-tone in said receiving instrument without aiecting the responsiveness of said receiving instrument or its circuits tc signaling waves received from distant stations.

9. In combination, an electric discharge tube having a cathode, .an anode and a control element, means to cause said tube to transmit a speech-modulated high frequency wave, a microphone circuit associated with said tube, a telephone receiver associated with said tube for receivin the speech frequency component of modu ated waves present in the circuit of said tube, and an antiside tone circuit between said microphone circuit and said receiver circuit for reducing the loudness of sounds produced in said receiver.

10. In combination, an electric discharge tube having a cathode, an anode and a control element, means to cause said tube to transmit a speech modulated high fre uenc wave, a microphone circuit asSOciate wit said tube, a telephone receiver associated with said tube for receivin the speech frequency component of modu ated waves present in the circuit of said tube, an anti-sde tone circuit between said microphone circuit and said receiver circuit, and means permitting said anti-side tone circuit to transmit current variations in only one direction. 11. In a two-way signaling system, an electric discharge tube having a cathode, an anode and a control element, a transmission circuit, a telephone transmitter and a telephone receiver, said tube being arranged with respect to the other mentioned elements to impress a high frequency wave on said transmission circuit modulated in accordance with speech waves from said telephone transmitter, and to receive from said transmission circuit s eech modulated high freuency waves an to impress on said receiver 4t e speech com onent of the received modulated waves an also speech waves from said telephone transmitter, and a circuit for reducmg the amplitude of the speech currents in said receiver originating in said telephone transmitter, said circuit comprising a connection between said telephone transmitter and said receiver containing means for permitting current transmisslon only in the direction from said transmitter to said receiver.

In witness whereof, I hereto -subscribe my name this 4th day of August A. D., 1920.

-- RAYMOND A. HEISING. 

